excellent post
okay...main problem is the router itself. it cant handle the 20meg afaik.
WPA does bugger up the speed a bit of the wlan network, has something to do with the kind of encryption it uses (please correct me if I'm wrong here but afaik it uses 256bits encryption)
which firmware you running now I presume 4.05.03 as thats the most up to date firmware for the 7230 v1000.
check your pm as well